1. Field of the Invention
The present invention generally relates to structural arrangements for supporting crankshafts in multicylinder engines, and more particularly, is directed to improvements in an arrangement for supporting a crankshaft to be rotatable by a plurality of bearing portions in a cylinder block of a multicylinder engine.
2. Description of the Prior Art
A multicylinder engine which is an internal combustion engine of the multicylinder type is provided therein with a plurality of bulkheads for forming a supporting structure for a crankshaft, and it is generally required of the multicylinder engine to reduce vibrations of each bulkhead caused in a direction along which the crankshaft extends due to revolutions of the crankshaft and noise resulting from the vibrations of the bulkhead. For the purpose of causing the multicylinder engine to fulfill such a requirement, there has been proposed to interconnect bearing portions each provided on the bulkhead for supporting the crankshaft through, for example, beam members so as to increase rigidity of the supporting structure for the crankshaft in the direction along which the crankshaft extends, as disclosed in, for example, the Japanese patent application published before examination under publication number 57-99248 and he Japanese Utility model application published before examination under publication number 59-34049.
In the crankshaft supporting arrangement disclosed in the above mentioned published Japanese patent application, a pair of beam members are incorporated with a plurality of bearing caps, each of which constitutes a bearing portion for supporting the crankshaft in conjunction with the bulkhead, and disposed to extend along the crankshaft at right and left lower side positions in the multicylinder engine, respectively. In the case of this arrangement, each adjacent two of the bearing caps are interconnected through each beam member and therefore each of the bulkheads, with which the bearing cap is coupled to form the bearing portion for supporting the crankshaft, is restrained from vibrating during revolution of the crankshaft. However, since each of the bearing caps is made large in size to keep the beam members sufficiently apart from the crankshaft so that the beam members are positioned at the outside of a space necessary for the revolution of the crankshaft, each of cap bolts used for clamping the bearing cap to the corresponding bulkhead is required to be made long and therefore it is difficult for the bearing cap to be coupled rigidly enough with the bulkhead.
Further, in the crankshaft supporting arrangement disclosed in the above mentioned published Japanese utility model application, each of the bearing caps constituting the bearing portion for supporting the crankshaft in conjunction with the bulkhead is coupled with a connecting plate member which is provided for interconnecting therethrough right and left side skirt portions of the cylinder block of the multicylinder engine, so that the connecting plate member is used as a beam member interconnecting therethrough the bearing caps. In the case of this arrangement, each adjacent two of the bearing caps are interconnected through a portion of the connecting plate member and therefore each of the bulkheads, with which the bearing cap is coupled to form the bearing portion for supporting the crankshaft, is restrained from vibrating during revolution of the crankshaft. However, since each of connecting bolts for fixing the connecting plate member to the bulkhead is also used as the cap bolt for clamping the bearing cap, which is positioned between the bulkhead and the connecting plate member, to the bulkhead, each of cap bolts, that is, each of the connecting bolts is required to be made long and therefore the bearing cap can not be coupled rigidly enough with the bulkhead also in this case.